Gaseous fuel feed systems for internal combustion engines



R. F. ENSIGN Jan. 13, 1959 GASEOUS FUEL FEED SYSTEMS FOR INTERNAL COMBUSTION ENGINES 2 Sheets-Sheet 1 Original Filed Dec. 9; 1952l IN V EN TOR.

.Illinoy EVS/6N,

Jan. 13, 1959 R. F. l-:NslGN 2,868,530

GASEoUs FUEL FEED SYSTEMS EOE INTERNAL coNEUSTroN ENGINES Original Filed Dec. 9, 1952 2 Sheets-Sheet 2 'lll/l. 'la '111111, Il

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GASEDUS FUEL FEED SYSTEMS FOR INTERNAL CMBUSTION ENGINES Roy F. Ensign, Fullerton, Calif., assignor to Ensign Carburetor Company, Huntington Park, Calif., a corporation of California 12 Claims. (Cl. ld-184i) The present invention has to do with gaseous fuel feed lsystems for fuel co-nsuming devices which `take their fuel via a fuel nozzle that is subjected to a fuel inspiring depression developed by the velocity of air flow. Typical, is an internal combustion engine fed with gaseous fuel via a fuel nozzle which is subjected to the velocity depression attendant the ilow of air drawn by the engine through the throat of a venturi. In such systems the gaseous fuel is fed tothe fuel nozzle under control of a pressure regulator which is adjusted to deliver fuel at a pressure slightly under the normal standing pressure of the effective surrounding atmosphere. Typically the regulator delivers its gaseous fuel to the fuel nozzle at a pressure of about one-quarter inch of water under the effective atmospheric pressure, to insure Aclosure of the regulator valve when the pressure in the delivery chamber becomes atmospheric with the engine standing.

The depression at the fuel nozzle in the venturi throat then has to be at least that one-quarter inch in order to draw in any fuel at all; and in the absence of some special provision, no fuel or insufficient fuel will be drawn in during starting turn-over or idlingoperation of the engine. Typically, starting fuel is provided by choking the air intake of the venturi; and idling fuel is provided via an idling bylpass which applies suction from the engine manifold inside the throttle to the regulator outlet.

The present invention utilizes a pressure drop due to a permanent obstruction in the air intake to modify the regulator action to make it deliver fuel at a higher than normal pressure, especially for starting and idling operations. Such an obstruction is preferably one that engenders a definite minimum pressure drop at minimum air ow; such for instance as a weighted air intake valve. In practice, the commonly used oil-bath type of air cleaner provides just such a weighted valve and such a pressure drop.` The invention utilizes such a` pressure drop to relatively increase the reference pressure which controls the pressure atwhich the regulator valve opens,

thereby to increase the delivery pressure of the regulator r but without correspondingly increasing the pressure being applied to the fuel nozzle to draw fuel.

4This application isa division of my application Ser. No. 324,986,` tiled December 9, 1952, now Patent No.

2,799,564. ln the forms of my invention comprising the subject matter of this divisional application, the change in reference pressure is applied to the regulator by the operation of an auxiliary diaphragm exposed on its oppo-` s site faces to the ambient atmospheric pressure and the reduced pressure due to the obstruction, acting typically through springs or` the equivalent.`

The invention as above generally outlined will be more fully understood from consideration of the following de- Atailed descriptions of illustrative embodiments shown in 2868,@ Patented Jan. 13, 1959 ICC 2 `Fig. 1n shows awlrnodication` of the device causing the pressure drop, in the'form of a simple weighted valve;

Fig. 2 shows ajnio'dication in such a system as shown in Fig. l;` and l", L"

Fig. 3 shows another modilication in such a system as shown in Fig. 1.`y l` Reference is `lirst made to the showings in Figs. 1 and 1n. Therein atypical` engine carburcter is schematically indicated, includinlga mixture passage 10 controlled by throttle 11, having a venturi 12 witha gas feed nozzle 13 deliveringat its throat..` x Mixture'passage 10"delivers tointake manifold 199i engine 20." Air intake passage 'le has balance passage'lL-ljin thefOrin of a Pitot tube, communicating with it to pick up the total air pressure; and the air intake ,is controlled, in Fig. 1.,"'byfth`e 1typical oil-bath c1`eaner'16. Sucha'cleaner typically involves an air tube" '17 having its lwer end submerged toladistance of,`sa'y,I one-half`inch, iiifoil bath"18`.. That distance representsthe pressure drop occurs in the cleaner at minimum (any) air "Above the oil bath the air :Hows th'rou'gh atilter plug 18a where the oil and dirt carried by the air"ai'c`ltered1out. For the purposes of the present invention it is only the pressure drop function of the cleaner that plays'a part; andthat function maybe perform-ed by any air intake device thatimposes a definite or suicicntly large pressuredrop at minimum air llow. Another such device is the weighted air intake valve `20a shown in Fig.` lul; where the weight of the valve may beso relatedto its effective air intake area as to provide the same pressure dropfsay /z inch water, as in the cleaner.

lnFig. 1, the essentials of a fluid pressure regulator arefillustratively shown,` includinga' pressure controlling valve 3l) operatedby diaphragm'32 which` has one face exposed tofoutlet` pressure in delivery chamber 34 and the otherv face exposedl in reference chamber 36 to the reference prs'sureflfkedup by tube 15.` The arrangement is such that pressure in 3'4tends to close valve 3l) and pressure `in 36 tends td 'open it. As" here shown illustratively in very simple form, valve 30 closes "in such a direction that pressurein'the initial intake 38 on 4the valve".` tends` to closeitj and a spring 40 `may also tend to'close it. Tlie"'c`losing'` spring may be omitted if desired, and the" valve"clo`sd fsimply by a regulated intake presjsre'o'n itl On the other hand,` the valve may be arranged, asforinstance shownin FigfB, "to close against the'inlet pressure'insteadff with itl In that arrangement, a spring" clb`se`s"the yalvefagainst the inlet press'uref And in'any ofthe various known arrangements vof the valve and it's` onnectionwith its operating diaphragm, 'the'various forces "are so adjusted and related that the'valve will"clos`e when pressures areequal in delivery chamber' 34 'and reference chamber 36, and will open whenthepre's'sure inchamber 34 is less than that in 36 by say`1i incliwaten `Ii1`"other`words, the normal valve closing fdrcejof spring 40` arid/orthe initial inlet pressur"`on `the"`valve, Vis equalto "the total force of a fluid `pressure of, say, 1Alinchof water on diaphragm 32. To insure the valve always openingf`witli`-`s`inall or no variation` from such'aset delivery pressure, the initial inletprelssur'e 'on valveSQf teddingeitherto closehor open itmsho'uld `preferably be we ll regulated, `a`s for instance by a regulator 'stage preceding theo-ne here illustrated. `I n Fig." `1,if referencepressure chamber 36 is simply connected tothe" same static pressure thatapplies to nozzle 13 (for instance',`if balanc'e tube 1 5 is simply connected fs chambers@ ghe relative velocity depression in thehventur'itliroat will not be lsuicient, at starting and on'idling, Atd 'open valve 30 at all',"`o`r enougl'to provide sufficient` fuel. I the forni shownin Fig."l` theinvention insures` that valve opening by thetfollowi'ng provisions.

A second diaphrgnifis exposed on one face" to starting will open the valve.

atmosphere in a chamber 44 and on its other face to the pressure in a chamber 46 which is in communication with reference pressure chamber 36 of diaphragm 32. 1n fact, chambers 36 and 46 are functionally one, being separated only by the perforated wall 48 which merely Vacts as a limiting stop for inward diaphragm movement.

Diaphragm 42 carries on its outer face a cage Si? enclosing a compression spring 52 whose one end is seated against a seat 54 adjustable by a screw 56 mounted in the cage. l Cage Sli, it may be noted, is imperforate so as not to afford a communication between 44 Aand 46. The other spring end seats on a seat 58 which, when diaphragm 42 is not drawn to the right by lowered pressure in 46, is pressed by the spring against the diaphragm. Undervthose conditions, when the engine is standing, diaphragm 42 floats freely with atmospheric pressure on both faces and consequently spring 52 exerts no pres- .sure on the` end of the extended valve stem 60, which extends from valve 30 and is secured in diaphragm 32. However, when the pressure in 46 is reduced suiciently ,below that in 44, diaphragm 42 is drawn to the right opening force which is adjustably set as to amount by l ythe setting of screw 56. Assuming, for example, that the effective areas of diaphragm 32 and 42 are equal and lthat the pressure drop in cleaner 16 or equivalent air 4intake obstruction is as great as or greater than the pressuredifferential on diaphragm 32 necessaryto open valve 30, then if the obstruction pressure drop is applied to chamber 46 to m-ove diaphragm 42 to the position shown, spring 52 can be adjusted to apply sufficient valve opening pressure to valve stem 60 to substantially equalize all the forces acting on the valve. In the illustration here given, valve 3G, standing, is closed by a force equal to 1A water on the effective area of diaphragm 32. The cleaner pressure drop, of say 1/2" water, applies twice that force to diaphragm 42 to move it to the position shown in Fig. 1. Spring 5 2 then applies to valve stem 60 an opening force that is, say substantially or justrequal to the 1A water on the diaphragm area. Under those circumstances the valve will then require only a very slight additional opening force to be exerted on it from diaphragm 32, or will be floating in equilibrium, or will be actually opened to some extent. It will suffice for this explanation and for proper operation that spring 52 be adjusted to exert on the valve an opening reference force substantially just equal to the normal valve closing force, which` substantially just iputs the valve oa'ting in equilibriumunder the forces tending to open and close it, excepting the differential force due to velocity depression in the venturi acting on the valve operating diaphragm 32.

vWhen the engine is standing, the pressures on the op- -posite faces of both diaphragms 32 and 42 are all atmospheric. Diaphragm 42 is therefore free and spring 52 exerts no opening reference pressure on valve 30. Diaphragm 32 is also free and valve 30 is therefore held closed by the set closing pressure. In the illustration here given that pressure is equal to a `differential of 1A water over j the effective face of diaphragm 32.

On turning over the engine to start, and drawing in air through the air cleaner or equivalent obstruction,a depression of say 1/2" water is applied to both the balanc-e tube 15 and fuel nozzle 13. Diaphragm 42 is drawn to the right, applying the valve opening 'pressure of spring 52. Diaphragm 32 is in substantial balance with the 1/2 depression applied to both faces. Valve 30 is either .thereby actually opened to deliver fuel to the nozzle or is put in equilibrium so that then the very slight venturi throat'depression applied to delivery chamber 34 during And on idling operation, the slight venturi throat depression will also `open the fuel valve to provide fuel in 'proportion to the air passing through the venturi. If a relativelyrich mixture is desired or necessary for starting and idling, SCICW 56 can be set so that valve 3@ instead of being put just in equilibrium by pressure of spring 52, will be positively opened when that spring pressure is applied.

With valve 3@ in balance, the pressure at which fuel is maintained in delivery chamber 34 and delivered to nozzle 13 will be substantially equal to the reference pressure in chamber 36. And that same condition of fuel delivery applies also to normal operation in all ranges; as the cleaner depression always operates to actuate diaphragm 42 as described. rl`hus, in normal operation of the engine in medium and higher ranges the fuel, supply will always be substantially if not exactly propery tionate to the air volume, because the pressure at which fuel is delivered to nozzle 13 will fbe always substantially the pressure which is picked up by Pitot balance tube l5 and transmitted as a reference pressure to diaphragm Fig. 2 shows a desirable modification of such a system as that shown in Fig. l. In any such system where the press-ure drop through such an oil filter air cleaner is utiliz-ed to increase the valve opening reference pres. sure, the oil in the cleaner may in some `circumstances not be in position to give that pressure drop for idling operation. lf the engine is operated for any length of time at wide open throttle and high speed the air tiow through the cleaner may carry all or most of the hydrostatic head of oil up into the filter 4plug where it will remain as long as the fast air flow continues. That condition does not affect pro-per operation of the regulator as long as fast air flow exists, as the pressure rop in the air cleaner at that air flow velocity is higher than the pressure drop at low lair velocities and the fuel pressure regulating valve therefore is kept in lproper operation. However, Vif the throttle is suddenly subsequently closed the engine will drop to idling speed before the cleaner oil can drop out of the lilter plug to provide the hydrostatic head necessary to give the required pressure dro-p at low air speeds. The arrangement of Fig. 2 overcomes that difficulty.

in Fig. 2, parts which are the same as in Fig. l, are given the same numerals. In Fig. 2 wall 48a between chambers 46a and Sinn is imperforate except for the passage 481) which passes and guides the valve stem 65. Chambers 36a and 46a are consequently separated from each other; and any leakage through 'lb around the valve stem is sealed off by a spherical valve` formation "42a carried by diaphragm 42 and seating on seat fafa when the diaphragm is in its operating [position as shown in the ligure. Balance tube 15a connects only to erence chamber 36a of diaphragm 32; land chamber 46c of Vdiaphragm 42 is connected by passage lh with the engine manifold by being connected directly to the manifold or to the mixture passage beyond the throttle.

The action on starting turn-over is the same as for Fig. 1. Both chambers 34 and 36a of diaphragm 32 are lsubjected to the cleaner depression via 15a and 13.

Chamber 46a of diaphragm 42 is subjected also to cleaner depression via the connection 15b, because regardless of throttle position that depression appears in the mixture passage (manifold) beyond the throttle. At starting lturn-over' the connection 15b picks up substantially the same total pressure as is picked up by Pitot tube 15. Diaphragm l2 is consequently drawn to the right as shown `in Fig. 2 with the same functional results on valve 30 as in Fig. l. And in the position of Fig. 2 the diaphragm valve V4i2a, seating on seat 48e cuts off any leakage which might otherwise take place from the air intake via 15a, 36a, and 48b to chamber 46a and thus to the engine manifold. Any suitable form of sealing means around the valve stem to seal off the leakage may of course be used either in addition to or in lieu of the sealing valve 42a.

During all phases of engine operation, diaphragm 42 will remain in its right hand position because, regardless of throttle position, the depression obtaining in the entube 15.

gine manifold is `always at least as great as the initial, yslow air-speed, depression of the air cleaner. At the high air velocity at wide open throttle `whichimay carry the cleaner oil up into the filter plug, the `manifold depression is greater than that caused by the hydrostatic head .at low velocity. And if the throttle is thensuddenly closed the manifold depression, even after `the engine speed falls to idling, is still greater than the depression due to the hydrostatic cleaner head. Diaphragm 42 consequently 4remains in operating position and continues `to impose the reference force of spring 52 on valve 315i, even though `the `cleaner may momentarily have lost the hydrostatic `head which gives the operative depression at low air speeds. Under all other operating conditions the cleaner depression of at least its hydrostatic head value is applied 4to the several chambers and diaphragms with the same results as in Fig. 1. l

Fig. 3 shows `another modication `of the devices of Fig. l. Here the main diaphragm 32 has at one face delivery chamber Eid which, as in Fig. 1, communicates with fuel nozzle 13'. The reference pressure chamber 36 is in communication or common with, diaphragm chamber lo of diaphragm 42, as in Fig. 1; and both chambers 3d and .d6 are again connected to Pitot balance (As will beco-me apparent, the modification of Fig. 2 is just as applicable to the form of this Fig. 3 as to that of Fig. l.) Chamber ld of diaphragm d2, as in Fig. l, is `open to atmosphere. Wall 48 between chambers 36 and lo `merely forms a stop for diaphragms l2 and 32.

Pressure regulating valve Stlb is carriedby a stirrup 30e on diaphragm 32 and closes onto its seat tld in a direction against the luid pressure'in initial inlet 38a, instead of with that pressure as in Fig. l. A spring 40h, adjustable by threaded plug dile, exerts a pressure tending to,

close the valve; preferably adjusted to exert substantially just that pressure which will balance the, preferably regulated, inlet fluid pressure on the `valve tending to open it.

A spring Si) bears on diaphragm 42 tending to move it to the left in the figure, that is, in a direction out of chamber 46. The two diaphragms are interconnected by a lost motion connection which will tend to move diaphragm 32 to the left, in its valve closing direction, when diaphragm d2 moves to the left. Any kind of lost motion will do, but as here illustrated, it is cornposed of two inter-engageable lingers 81 and 82 carried by the respective diaphragms. When atmospheric pressure attains in all the diaphragm chambers, when the engine is standing, the parts assume the positions shown in the ligure and the pressure of spring titl is applied, via the lost motion connection, to valve 30h in a closing direction. The valve is thus held closed by the force of that spring; which may be considerable, as it may be anything less than the total force which will be exerted on the area of diaphragm i2 by the depression caused by the air cleaner or equivalent obstruction in the air inlet. In this connection it is also remarked that, in Fig. l, the normal (standing) closing force exerted on valve 30 may be anything less than the total force that will be exerted on diaphragm 42 the pressure drop of the cleaner or equivalent; spring 52 being adjustedaccor-dingly.

On starting turn-over and on idling operation, both balance tube 15 and nozzle 13 are subjected to the depression of the cleaner or equivalent. Diaphragm 42 is drawn to the right and the pressure of spring 80 is taken olf valve 3%. The valve then floats in substantial equilibrium and a slight velocity depression at the venturi will then open it. The operation is then the same as in Fig. l.

Functionally, the devices of Figs. 1 and 3 are in substance the same. in both devices the operation of diaphragm 42, by cleaner or equivalent pressure drop, changes the forces acting on the pressure regulating valve system so as to put that valve in substantial equilibrium. In both it may be said either that a reference pressure tending to open the valve is etfectively added to the forces acting on theivalve, or that a valve closing pressure is effectively removed. ln 3 an opening force is elfectively added by taking away a closing force; in Fig. l, a closing force is effectively taken away by adding an opening force.

In all of the several forms described, use is made of the dropped or diminished pressure due to the air intake obstruction, that is, of the difference between that pressure and `that of the effective surrounding atmosphere; or, for short, of the drop in pressure due `to the obstruction (e. g. cleaner). That pressure drop is utilized in all the various forms `to control, in one manner or another, the application to the regulating `valve of an effective valveopening reference pressure which is greater than that exerted onthe valve operating diaphragm by the obstruction-diminished pressure; the measure ofthe excess reference pressure being the force by which the regulating valve is normally closed.

l claim:

1. In gaseous fuel feed systems for internal combustion engines `and the like, the combination of an air and mixture `passage having an outlet to the engine intake manifold, an air `intake and a venturi throat between intake and outlet, a permanent obstruction in the air intake positively imposing a pressure reduction with relation to atmospheric pressure on the air passing therethrough at minimum flow, a gas pressure regulator comprising `a pressure `regulating valve controlling gas flow from an initial inlet to a delivery chamber, a diaphragmvalve system including said valve and a valve operating diaphragm having one face exposed to fluid pressure in the delivery chamber and the other face exposed toiiuid pressure in a reference chamber, the fluid pressure in the `delivery chamber exerting a force on said diaphragm tending to move it in a valve closing direction and the iluid pressure in the reference chamber exerting a force on said diaphragm tending to move it in a valve opening direction, means `normally applying an additional definite closing force to the valve whereby the valve is normally closed with a -denite pressure when fluid pressures on opposite faces of -the valve operating diaphragm are equal, a gas delivery passage leading from the delivery chamber to the venturithroat, an auxiliary diaphragm expo-sed on one face tothe ambient atmospheric pressure and on its opposite face to the pressure in an auxiliary diaphragm chamber, means applying to `the reference chamber and to the `auxiliary diaphragm chamber the pressure existent in the air and mixture passage downstream of the air intake obstruction, and means actuated by movement of the auxiliary diaphragm into the auxiliary diaphragm chamber to effectively decrease the valve closing pressure exerted on the valve by the valve closing means.

2. The combination defined in claim 1, including also a throttle in the air and mixture passage down-stream of the venturi throat, and in which the means which applies the pressure existent in the air and mixture passage to hte reference chamber and to the auxiliary diaphragm i chamber comprises a single passage means picking up the pressure existent in the air and mixture passage between the obstruction and the throttle.

3. The combination defined in claim ll, including also a throttle in the air and mixture passage down-stream of the venturi throat, and in which the means which applies the pressure existent in the air and mixture passage to the reference chamber and to the auxiliary diaphragm chamber, comprises a passage means picking up the pressure existent in the air and mixture passage between the obstruction and the throttle and applying that pressure to the reference chamber, and another passage means picking up the pressure in the air and mixture passage down-stream of the throttle and applying that pressure to the auxiliary diaphragm chamber.

4. The combination defined in claim l., including also a lost-motion connection between the valve and the auxiliary diaphragm whereby valve closing pressure is exerted on the valve by virtue of the auxiliary diaphragm moving in a direction away from its chamber, and in which the valve-closing means includes a spring exerting pres- Y sure on the auxiliary diaphragm tending to move it in said direction.

5. The combination defined in claim 4, including also a thro-ttle in the air and mixture passage down-stream of the venturi throat, and in which the means which ap plies the pressure existent in the air and mixture passage to the reference chamber and to the auxiliary diaphragm chamber comprises a single passage means picking up the pressure existent in the air and mixture passage between the obstruction and the throttle.

6. The combination defined in claim 4, including also a throttle in the air and mixture passage down-stream of the venturi throat, and in which the means which ap* plies the pressure existent in the air and mixture passage to the reference chamber and to the auxiliary diaphragm chamber comprises a passage means picking up the pressure existent in the air and mixture passage between the obstruction and the throttle and applying that pressure to the reference chamber, and another passage means picking up the pressure in the air and mixture passage down-stream of the throttle and applying that pressure to the auxiliary diaphragm chamber.

7. In gaseous fuel feed systems for internal combustion engines and the like, the combination of an air and mixture passage having an outlet to the engine intake manifold, an air intake and a venturi throat between intake and outlet, a permanent obstruction in the air intake positively imposing a pressure reduction with relation to atmospheric pressure on the air passing therethrough at minimum flow, a gas pressure regulator comprising a pressure regulating valve controlling gas flow from an initial inlet to a delivery chamber, a diaphragm-Valve system including said valve and a valve operating diaphragm having one face exposed to fluid pressure in the delivery chamber and the other face exposed to fluid pressure in a reference chamber, the fiuid pressure in the delivery chamber exerting a force on said diaphragm tending to move it in a valve closing direction and the uid pressure in the reference chamber exerting a force on said diaphragm tending to move it in a valve opening direction, means normally applying an additional definite force to the diaphragm-valve system whereby the valve is normally closed with a definite pressure when uid pressures on opposite faces of the valve operating diaphragm are equal, a gas delivery passage leading from the delivery chamber to the venturi throat, an auxiliary diaphragm exposed on one face to the ambient atmos- Ypheric pressure and on its opposite face to the pressure in an auxiliary diaphragm chamber, means applying to the reference chamber and to the auxiliary diaphragm chamber the pressure existent in the air and mixture passage down-stream of the air intake obstruction, said Valve closing means including a spring exerting pressure on the auxiliary diaphragm tending to move that diaphragm in a direction out of its chamber, and a lost motion connection between the auxiliary diaphragm and the diaphragmvalve system applying valve closing force when the auxiliary diaphragm moves in said direction.

8. The combination defined in claim 7, including also a throttle in the air and mixture passage down-stream of the venturi throat7 and in which the means which applies the pressure existent in the air and mixture passage to the reference chamber and to the auxiliary diaphragm chamber comprises a single passage means picking up the pressure existent in the air and mixture passage between the obstruction and the throttle.

9. The combination defined in claim 7, including also a throttle in the air and mixture passage down-stream of the venturi thro-at, and in which the means which applies the pressure existent in the air and mixture passage to the reference chamber and to the auxiliary diaphragm chamber comprises a passage means picking up the pressure existent in the air and mixture passage between the obstruction and the throttle and applying that pressure to the reference chamber, and another passage means picking up the pressure in the air and mixture passage down-stream of the throttle and applying that pressure to the auxiliary diaphragm chamber.

10. The combination defined in claim l, and in which the last mentioned means includes a spring operatively controlled by movements of the auxiliary diaphragm to apply and to remove spring force to and from the pressure regulating valve.

11. The combination detined in claim 1, and in which the last mentioned means includes a spring through which valve opening pressure is applied to the valve by movement of the auxiliary diaphragm into its chamber.

12. The combination defined in claim 1l, and in which said spring is carried by the auxiliary diaphragm.

References Cited in the file of this patent UNITED STATES PATENTS Ensign `luly 16, 

1. IN GASEOUS FUEL FEED SYSTEMS FOR INTERNAL COMBUSTION ENGINES AND THE LIKE, THE COMBINATION OF AN AIR AND MIXTURE PASSAGE HAVING AN OUTLET TO THE ENGINE INTAKE MANIFOLD, AN AIR INTAKE AND A VENTURI THROAT BETWEEN INTAKE AND OUTLET, A PERMANENT OBSTRUCTION IN THE AIR INTAKE POSITIVELY IMPOSING A PRESSURE REDUCTION WITH RELATION TO ATMOSPHERIC PRESSURE ON THE AIR PASSING THERETHROUGH AT MINIMUM FLOW, A GAS PRESSURE REGULATOR COMPRISING A PRESSURE REGULATING VALVE CONTROLLING GAS FLOW FROM AN INITIAL INLET TO A DELIVERY CHAMBER, A DIAPHRAGMVALVE SYSTEM INCLUDING SAID VALVE AND A VALVE OPERATING DIAPHRAGM HAVING ONE FACE EXPOSED TO FLUID PRESSURE IN THE DELIVERY CHAMBER AND THE OTHER FACE EXPOSED TO FLUID PRESSURE IN A REFERENCE CHAMBER, THE FLUID PRESSURE IN THE DELIVERY CHAMBER EXERTING A FORCE ON SAID DIAPHRAGM TENDING TO MOVE IT IN A VALVE CLOSING DIRECTION AND THE FLUID PRESSURE IN THE REFERENCE CHAMBER EXERTING A FORCE ON SAID DIAPHRAGM TENDING TO MOVE IT IN A VALVE OPENING DIRECTION, MEANS NORMALLY APPLYING AN ADDITIONAL DEFINITE CLOSING FORCE TO THE VALVE WHEREBY THE VALVE IS NORMALLY CLOSED WITH A DEFINITE PRESSURE WHEN FLUID PRESSURES ON OPPOSITE FACES OF THE VALVE OPERATING DIAPHRAGM ARE EQUAL, A GAS DELIVERY PASSAGE LEADING FROM THE DELIVERY CHAMBER TO THE VENTURI THROAT, AN AUXILIARY DIAPHRAGM EXPOSED ON ONE FACE TO THE AMBIENT ATMOSPHERIC PRESSURE AND ON ITS OPPOSITE FACE TO THE PRESSURE IN AN AUXILIARY DIAPHRAGM CHAMBER, MEANS APPLYING TO THE REFERENCE CHAMBER AND IN THE AIR AND MIXTURE PASSAGE DOWNSTREAM OF THE AIR TO THE AUXILIARY DIAPHRAGM CHAMBER THE PRESSURE EXISTENT INTAKE OBSTRUCTION, AND MEANS ACTUATED BY MOVEMENT OF THE AUXILIARY DIAPHRAGM INTO THE AUXILIARY DIAPHRAGM CHAMBER TO EFFECTIVELY DECREASE THE VALVE CLOSING PRESSURE EXERTED ON THE VALVE BY THE VALVE CLOSING MEANS. 